Air separation modules are designed to separate one or more components, such as an inert gas, from air. By separating an inert gas, such as nitrogen, from air, the inert gas can be utilized for various purposes. For example, the inert gas may fill an environment that may be flammable or unstable if the environment were otherwise filled with air and subjected to a spark or other ignition source. For example, an air separation module may produce nitrogen that is utilized to fill the ullage or headspace within a fuel tank so as to reduce the possibility of an explosive event.
An air separation module generally includes a plurality of hollow fiber membranes. The opposed ends of the hollow fiber membranes may be affixed relative to one another by a tubesheet. An air separation module tubesheet may be formed of a tubesheet potting matrix that surrounds end portions of the hollow fiber membranes so as to secure the hollow fiber membranes in position and to prevent the passage of air around the hollow fiber membranes with the air, instead, being forced through the hollow fiber membranes. A hollow fiber membrane may be constructed of a material, such as polysulfone, that preferentially permits oxygen and moisture to pass through the membrane walls while maintaining the inert gas, such as nitrogen, within the hollow fiber membrane, thereby separating the inert gas enriched air from the oxygen enriched air.
The exposure of the tubesheet potting matrix of an air separation module tubesheet to air at elevated temperatures and, more particularly, to moisture and/or contamination, such as ozone, within the air may cause the matrix to be degraded. In this regard, cracks may form in the matrix over time following exposure to air with some of the air thereafter passing through the cracks in the matrix as opposed to propagating through the hollow fiber membranes. In instances in which air passes through the cracks of the air separation module tubesheet, the air separation module may perform less efficiently, such as by not cleanly separating the inert gas from the air and, in some instances, producing less inert gas in response to the receipt of the same quantity of air.
Techniques have therefore been developed to inspect air separation module tubesheets in order to determine if an air separation module tubesheet has degraded, such as by the development of cracks within the air separation module tubesheets. These inspection techniques generally require the air separation modules to be removed from service for an evaluation that is conducted by an expert. By requiring that the air separation module be taken out of service and inspected by an expert, the techniques for inspecting air separation modules are generally more costly and time-consuming than may be desired.